1. Field of the Invention
The present invention relates to silicon carbide substrates and methods of manufacturing the same, and more particularly to a silicon carbide substrate capable of forming a device of excellent performance, and a method of manufacturing the same.
2. Description of the Background Art
A silicon carbide substrate has been used to manufacture a semiconductor device in recent years. Silicon carbide has a wider band gap than silicon, which is a more common material. Thus, a semiconductor device including a silicon carbide substrate has advantages including high breakdown voltage, low on-resistance, and high resistance to performance degradation in a high temperature environment.
It has been conventionally proposed to use a silicon carbide substrate having a reduced density of crystal defects, in order to realize a semiconductor device of excellent performance as described above. For example, U.S. Pat. No. 7,314,520 discloses a silicon carbide substrate having a screw dislocation density of less than about 2000 cm−2. U.S. Pat. No. 7,314,521 discloses a silicon carbide substrate having a diameter of at least about 100 mm and a micropipe density of less than about 25 cm−2. U.S. Pat. No. 7,294,324 discloses a silicon carbide substrate having a diameter of at least about 75 mm and at least one continuous square inch (6.25 cm2) of surface area that has a basal plane dislocation density of less than about 500 cm−2.
As a result of diligent studies by the present inventors, however, it has been found difficult to stably improve the performance of a device formed on a silicon carbide substrate by suppressing only the defects disclosed in these prior art documents. In addition, these prior art documents merely disclose general methods of manufacturing a silicon carbide substrate, and it is difficult to stably manufacture silicon carbide substrates having a low defect density as described above with these methods.